1. Field of the Invention
This invention relates to the field of preparing polyether polyols. More particularly, this invention relates to the use of isocyanurate catalysts in promoting oxyalkylation of specific alcohols.
2. Description of the Prior Art
Alkylene oxide adducts of various alcohols, aminoalcohols, etc. are well known and widely used in a variety of industries. Such polyoxyalkylene polyhydric compounds are particularly useful in making polyurethane compositions and/or polyisocyanurate polymers. The polyether polyol reacts with a polyisocyanate in the presence of a catalyst to prepare the polymers, particularly in foam form. When a polyisocyanurate foam is desired, the polyol-polyisocyanate polymerization is carried out by resort to an isocyanurate group formation catalyst which is used to trimerize the isocyanate groups to form the isocyanurate linkages.
The polyether polyols are generally prepared by the catalytic addition of an alkylene oxide or mixture of alkylene oxides, either simultaneously or sequentially to an organic compound usually having at least two active hydrogen atoms. The alkoxylation catalyst may be alkaline, neutral or acid, with an alkaline catalyst, such as an alkali metal hydroxide being most preferred. In a commerical operation, the usual catalysts are either sodium hydroxide or potassium hydroxide.
However, alkoxylation catalysts of this type have a number of drawbacks. Paramount among these is the requirement that the base employed after the alkoxylation reaction is completed be neutralized. The resultant salt must then be filtered from the polyol. This filtration step, of course, adds considerable cost and time to the overall process.
It would, therefore, be an advantage in the art if a catalyst were found which would overcome the just mentioned deficiency. It would be a further advantage if such portion of the catalyst which remains unused after the alkoxylation reaction could somehow be of further use in preparing polymer products which employ such polyether polyols.
Therefore, it becomes a principal object of the present invention to provide a method of making polyether polyols useful in preparing polyisocyanurate polymers, which polyether polyol method avoids the just discussed prior art drawback of employing conventional catalysts such as potassium hydroxide or sodium hydroxide. Other objects will appear hereinafter.